This is wrong. In the 1970s there was for instance a big revival of ragtime, popular music from 50-60 years ago (then). Then there was of course the blues and v

This is wrong. In the 1970s there was for instance a big revival of ragtime, popular music from 50-60 years ago (then). Then there was of course the blues and various other folk revivals, which had a tremendous influence on all that 1965-75 music which is still popular. But of course there were both technical and copyright reasons they didn't just re-release recordings from the 20s!